Method of forming fire retardant panels



METHOD OF FORMING FIRE RETARDANT PANELS Filed Feb. 11, 1966 NTOR ' INVE Geolge F. Wilhelm BY [Zw /W United States Patent 3,480,494 METHOD OF FORMING FIRE RETARDANT PANELS George F. Wilhelm, Oak Park, Ill., assignor to R. S. Bacon Veneer Company, Chicago, 11]., a corporation of Illinois Filed Feb. 11, 1966, Ser. No. 526,747 Int. Cl. B32b 21/04, 31/12; C09j /06 US. Cl. 15690 3 Claims ABSTRACT OF THE DISCLOSURE The method of preparing a fire resistant panel which includes securing a thin layer of cross banded veneer to an asbestos-fiber core by an adhesive which is allowed to cure, then reducing the thickness of the cross-banded veneer to a thin film, followed by application of an adhesive thereon for securing a decorative face veneer thereover.

been produced previously have had the disadvantage of not being highly resistant to flame spread and of being stained owing to bleed through of the adhesive bonding the decorative face veneer to the core. Such staining occurs with the last named type of core because the adhesive used must be of a nature to penetrate and seal the asbestos-like core and must overcome the alkaline problem inherent when a lime-containing cement-asbestos core is used. Such an adhesive will bleed through and stain the face veneer. In other instances, thick layers of soft inexpensive wood and thin sheets of asbestos paper have been interposed between a balsa wood core and a veneered panel for the purpose of providing a sound deadening board. This type of board is heavy and bulky and has little or no resistance to flame spread.

To overcome such objectional bleed through and staining of the decorative face veneer in a fire retardant panel, applicant provides an intermediate layer of wood veneer cross banding between the cement-asbestos base and the decorative face veneer. In order to accomplish this without building up a panel of excessive weight and thickness, and to minimize flame spread, applicant has adhesively applied over the cement-asbestos core, on one or both sides, a very thin layer of wood veneer crossbanding. After the adhesive, preferably phenol-resorcinol resin or its equivalent, has cured and the bleeding has, therefore, stopped, the thin layer of wood veneer cross banding is further reduced in thickness to that of a thin skin without exposing the cement-asbestos core or the layer of adhesive bonding the wood veneer cross-banding to the core. This produces a well sealed core over which a second adhesive (such as melamine-fortified urea resin) is then applied and the sheet of decorative face veneer and a balancing back veneer (optional) are laid over opposed faces and the whole is pressed together in a hot plate press. This last named adhesive adheres to the wood surfaces and does not have bleeding characteristics, hence, the finished panel is devoid of stains, and is of minimum thickness while affording maximum strength and exposing a minimum amount of wood body to support flame spread.

3 480494 Patented Nov. 25, 1969 staining of the face veneer and to minimize flame spread.

Another object is to provide a novel method for manufacturing a veneered fire retardant panel.

Another object is to provide a panel of the character referred to which is neither expensive nor difficult to produce and one which is very efficient for the purposes intended.

The structure and method by means of which the above noted and other objects and advantages: of the invention are attained will be described in the following specifications, taken in conjunction with the accompanying drawings, showing a preferred illustrative embodiment of the invention, in which:

FIG. 1 is a perspective view of a panel fabricated by the within disclosed method, showing parts broken away.

FIG. 2 is an enlarged fragmentary sectional view of a partially fabricated panel.

FIG. 3 is a similar sectional view of the finished panel.

Referring to the exemplary disclosure in the accompanying drawings, the laminated panel is comprised of a core 11, and a ply of decorative face veneer 12, adhered to one side with a balancing backing veneer 12a, 0n the opposite side (optional). The core 11 is comprised of a mixture of cement with asbestos fibers pressed into the desired thickness and set. This type of material affords a hard, rigid, dense, non-combustible core.

In the fabrication of the finished product, the cementasbestos board or core 11 is coated on each surface with a layer 13 of adhesive, such as phenol-resorcinol resin or its equivalent, which has the capacity of soaking into the core so as to afford a good bond. Over each face is laid a sheet 14 (preferably not more than A inch in thickness) of wood veneer cross-banding, all of which is pressed firmly in place in a hot plate press and allowed to dry thoroughly. The nature of the adhesive used is such that it will bleed through the wood veneer cross-banding 14, thus staining same. However, since this is an innerply in the finished panel, the stain is of no consequence. The Wood veneer cross-banding layer 14 then is reduced in thickness as by sanding. This sanding continues to the extent that the wood veneer cross-banding has been reduced to a minimum thickness without exposing core 11, or the adhesive bonding the wood veneer cross-banding to the core.

A layer 16 of another adhesive, such as melaminefortified urea resin or its equivalent, which is also capable of withstanding fire testing without failure of bond, is applied to the sanded surface of the remaining thin film of wood veneer cross-banding 14. Over this, on one side, is laid the decorative face veneer 12 and on the other side, the balancing backing veneer 12a (optional). The adhesive 16 is of a character that does not bleed through, consequently there is no staining of the decorative face veneer 12 or veneer 12a. The whole is then pressed and cured in a hot plate press and subsequently trimmed to the required size. The cured product then is sanded and polished as may be required.

I claim:

1. The method of producing a fire retardant panel having a low degree of flame spread which consists of applying an alkali resistant resin adhesive to a surface of a core comprised of cement and asbestos fibers, adhering a layer of wood veneer cross banding thereover, allowing said adhesive to bleed into the wood veneer cross banding and cure, reducing the thickness of the thin layer of wood veneer to a thin film, applying a melamine-fortified 2,456,006 12/ 1948 Hickler 156 9Q urea resin to the surface of said skin, and adhering a 2,720,478 10/1955 Hogg 156154 decorative face veneer thereover. 2,859,187 9 8 P p l 161168 XR 2. The method recited in claim 1, in which the as- 3,196,494 7/1965 Hartman et a1. 161-413 XR sembly is hot pressed. 5 3,255,063 6/1966 Henneman 15 687 3. The method recited in Claim 1, inw'hich the thick} ness of the layer of wood veneer cross-banding is reduced ROBERT F. BURNETT, Primary Examiner by sanding-i v v References Cited 7 I W. A. POWELL, Assistant Examiner 'UNITED STATES PATENTS 10 US. C1.X.R. 2,028,076 1/1936'N0rris 156-155 15 6'75; 154; 161-56, 205, 403

2,173,808 9/1 939 Kellogg. 

